Simulated
severe thunderstorm, first view.Data
from Crystal Shaw and Bob Wilhelmson. The orange contour lines are for
vertical wind velocity, contoured at 3 m/sec. Vertical wind velocity is also
mapped as the color onto the rain water isosurface contoured at 6 grams per
grams of air. It also looks like the rainbow color map goes from purple
(downdraft) to red (updraft).

The
NCSA Atmospheric/Oceanic Sciences Group, led by Dr. Robert Wilhelmson, is
collaborating with Professor Mohan Ramamurthy of the University of Illinois
Atmospheric Sciences Department in studies of the development and impact of
Hurricane Opal. Opal, which reached Category 4 status with winds exceeding
150 mph prior to landfall, struck near Pensacola,
Florida on Oct. 4, 1995. Along
its path, Opal produced over 10 inches of rain in parts of Florida,
Alabama and Georgia, and spawned 22
tornadoes. The storm caused extensive damage (over $3 billion dollars) and
resulted in 59 deaths (9 in the U. S.). Given the population growth and
development along its coasts, the U. S. is more vulnerable than
ever to damage from hurricanes. Adding to this vulnerability is a lack
of skill for forecasts of the timing, intensity of wind, and rain near
landfall. Hurricane track prediction is perhaps one of the simplest and
yet may become one of most important applications ensemble forecasting.
Similarly, the prediction of hurricane intensity change (e.g. central
pressure and peak tangential winds), one of the most difficult problems
confronting the hurricane prediction community, can benefit from ensemble
forecasting due to the many uncertainties in the description of processes influencing
tropical cyclone intensity change in NWP models. Professor Ramamurthy has
carried out a number of low-resolution simulations with the NCAR-Pennsylvania
State University MM5 model as part of a study of forecast sensitivity,
including the role of model initialization and physics, on hurricane track
and intensity. The NCSA Atmospheric/Oceanic Sciences Group has previously
carried out one higher (5 km horizontal) resolution simulation and is
preparing to make an even higher resolution run in order to better model the
observed landfall location of the hurricane and the associated heavy
precipitation accompanying it. Ultimately the model-predicted rainfall is to
be used with a runoff model to simulate the actual flooding that took place
on this day, and still higher resolution simulations (incorporating
additional nested grids) are anticipated. In addition, further visualization
in the CAVE is planned to better study the structure and evolution of the eye
at high resolution and the changes that occurred as the storm approached
land, weakening from a category 4 storm when it was farther offshore. The
combination of software (MM5/runoff connections) and hardware (CRAY
Origin2000) technology and CAVE visualization will allow us to better
simulate and understand the storm and its impact on the U.S.
mainland. Other
noteworthy sites:http://www.caps.ou.edu/